邮件服务器记录nslookup -qt=MX x.com
e?e=x.com

Array
(
    [0] => Array
        (
            [host] => x.com
            [type] => MX
            [pri] => 5
            [target] => alt2.aspmx.l.google.com
            [class] => IN
            [ttl] => 300
        )

    [1] => Array
        (
            [host] => x.com
            [type] => MX
            [pri] => 5
            [target] => alt1.aspmx.l.google.com
            [class] => IN
            [ttl] => 300
        )

    [2] => Array
        (
            [host] => x.com
            [type] => MX
            [pri] => 10
            [target] => alt4.aspmx.l.google.com
            [class] => IN
            [ttl] => 300
        )

    [3] => Array
        (
            [host] => x.com
            [type] => MX
            [pri] => 1
            [target] => aspmx.l.google.com
            [class] => IN
            [ttl] => 300
        )

    [4] => Array
        (
            [host] => x.com
            [type] => MX
            [pri] => 10
            [target] => alt3.aspmx.l.google.com
            [class] => IN
            [ttl] => 300
        )

)